Three-dimensional printing, also known as additive manufacturing, is a process of making a three-dimensional solid object from a digital model of virtually any shape. Many three-dimensional printing technologies use an additive process in which an additive manufacturing device forms successive layers of the part on top of previously deposited layers. Some of these technologies use extrusion printing in which an extrusion printhead emits a melted build material, such as heated and softened ABS plastic, in a predetermined pattern. The printer typically operates the extrusion printhead to form successive layers of the build material that form a three-dimensional printed object with a variety of shapes and structures. While printing each layer of the three-dimensional printed object, the extrusion printhead emits build material that cools and hardens after extrusion from the printhead to form another layer of the three-dimensional printed object. Three-dimensional printing is sometimes called additive manufacturing and is distinguishable from traditional object-forming techniques, which mostly rely on the removal of material from a work piece by a subtractive process, such as cutting or drilling.
Many existing three-dimensional printers use a single printhead that extrudes material through a single nozzle. The printhead moves in a predetermined path to emit the build material onto selected locations of a support member or previously deposited layers of the three-dimensional printed object based on model data for the three-dimensional printed object. However, using a printhead with only a single nozzle to emit the build material often requires considerable time to form a three-dimensional printed object. Additionally, a printhead with a larger nozzle diameter can form three-dimensional printed object more quickly but loses the ability to emit build material in finer shapes for higher detailed objects while nozzles with narrower diameters can form finer detailed structures but require more time to build the three-dimensional object.
One solution known to the art to increase printer throughput and provide high-resolution printing includes a single printhead with removable nozzles that have multiple diameters for higher throughput or higher precision operations, but such solutions require a unit to switch nozzles and still only provide a single nozzle to emit the build material. Another solution that is known to the art incorporates multiple independent printheads in a single printer. However, the multiple independent printheads increase the complexity of the printer and each printhead requires a separate supply of build material during operation. Furthermore, existing extrusion printheads require activation and deactivation of heaters and drive motors to start and stop the extrusion of build material, which reduces the precision of extruding the build material during operation or reduces the speed at which the printheads form different arrangements of build material. Consequently, improvements to extrusion printheads and methods for the operation of extrusion printheads during three-dimensional object formation processes would be beneficial.